This invention relates generally to microelectromechanical (MEMS) devices and, more particularly, to MEMS devices having movable mirrors used, e.g., in optical switches, scanners, projectors, etc.
Optical switches may be used for routing optical signals in fiber optic networks. The switches may selectively transmit light signals from a set of input fibers to a set of output fibers. The switches may include at least one array of movable mirrors or reflectors that can be selectively actuated to deflect light signals to particular output fibers. The movable mirrors can be actuated or controlled in a variety of ways including electromagnetic actuation, electrostatic actuation, piezoelectric actuation, or thermal bimorph. Fabrication of the mirror arrays has been attempted using MEMS technology, in which silicon processing and related techniques common to the semiconductor industry are used to form microelectromechanical devices.
In many applications for optical micromirrors, it is desirable to build an array of mirrors with both a high fill factor and control of two axes of rotation. Advantages of increased linear mirror fill factor include improved channel shape in wavelength division multiplexing systems and reduced optical loss. Advantages of having two axes of rotation over only one axis include the ability to more ably move the mirror in different directions, for example to steer an optical beam to hit or avoid a particular optical fiber.
For purposes of the instant invention, linear fill-factor as a term of art is defined as the size of the mirror in one direction divided by the pitch of the mirror array in the same direction.
One technique known in the prior art for achieving two axes of rotation has a mirror with a gimbals structure. This solution however, generally limits the fill factor achievable due to the area taken up by the gimbals.
A need exists for building an array of mirrors achieving both a high fill factor and control of two axes of rotation.
A need exists for obtaining fill factors in excess of 80%.
One aspect of the invention is a mirror device for obtaining dual axis rotation including a first means for electromagnetic actuation about a first axis; and a second means for actuation about a second axis where the first and second means for actuation do not utilize a gimbal structure. The first means for electromagnetic actuation utilizes at least one first coil. In another aspect of the invention, the second means for actuation is electromagnetic actuation utilizing at least one second coil. In another aspect of the invention, the at least one first coil and the at least one second coil can be positioned anywhere relative to each other on any side of the first and second axes. And in another aspect of the invention, the at least one first means coil is positioned only on one side of the first axis. Additionally, the at least one second means coil is positioned on the same side of the first axis as the at least one first means coil. And in another aspect of the invention, only the at least one second coil is present.
In yet another aspect of the invention, at least one permanent magnet provides a magnetic field to actuate the coils. Yet still another aspect of the invention includes an array formed of mirror devices with the first and second means for electromagnetic actuation providing a linear fill factor greater than 80%. Further aspects include an array of magnets of alternating polarity arranged to provide a magnetic field for the array of mirror devices and an array of center mirrors of the mirror device array having no coils.
In another aspect of the invention, the second means for actuation is electrostatic actuation utilizing at least one electrode. In yet another aspect of the invention, the at least one first coil and the at least one electrode can be positioned anywhere relative to each other on either side of the first and second axes. In a different aspect, the at least one electrode is positioned only on one side of the first axis. Additionally, the at least one coil is positioned on the same side of the first axis as the at least one electrode. And in another aspect of the invention, the at least one electrode is positioned only on one side of the second axis. Further aspects include the second means for electrostatic actuation utilizing a common ground plane, an interposer or at least one patterned electrode. Still further aspects include at least one permanent magnet providing a magnetic field to actuate the coils. In other aspects, an array formed of the mirror devices with the first and second means for actuation provides a linear fill factor greater than 80% and an array of magnets of alternating polarity is arranged to provide a magnetic field for the array of the mirror devices and wherein an array of center mirrors of said mirror device array includes no coils or electrodes.
In yet another aspect of the invention, the mirror device has a double paddle structure. And in still further aspects, the at least one electrode is used to sense rotation about at least one of the axes, a plurality of electrodes are used to measure differential capacitance for second axis rotation, or a plurality of electrodes on an interposer are used to measure differential capacitance for second axis rotation.
In another aspect of the present invention, a mirror device for obtaining dual axis rotation includes a first means for electromagnetic actuation about a first axis and a second means, coupled to the first axis, for electrostatic actuation about a second axis. In further aspects, the first means for electromagnetic actuation utilizes at least one coil and at least one permanent magnet provides a magnetic field to actuate the at least one coil. Other aspects include, the second means for electrostatic actuation utilizes at least one electrode, a common ground plane, an interposer, and/or at least one patterned electrode. Still further aspects include an array of devices with the first means for electromagnetic actuation and the second means for electrostatic actuation allowing for a linear fill factor greater than 80% and wherein an array of magnets of alternating polarity are arranged to provide a magnetic field for the mirror device array. In another aspect, an array of center mirrors of the mirror device array has no coils or electrodes. In yet another aspect of the invention, this mirror device has a double paddle structure. In still further aspects of the invention, the at least one electrode is used to sense rotation about at least one of the axes, a plurality of electrodes are used to measure differential capacitance for second axis rotation, or a plurality of electrodes on the interposer are used to measure differential capacitance for second axis rotation.
In still yet another aspect of the invention, an array of MEMS devices, where each device includes a mirror with a reflective surface having no gimbal support, at least one first coil for causing selective movement of the mirror about a first axis in the presence of a magnetic field, and means for causing selective movement of the mirror about a second axis. Further aspects include the means for causing selective movement utilizing at least one second coil in the presence of a magnetic field, the at least one first coil positioned in any position on each side of the first axis, the at least one first coil positioned only on one side of the first axis, the at least one second coil positioned in any position on each side of the second axis, the at least one first and second coils are superposed on the mirror, and/or the at least one first and second coils are not superposed on the mirror. Still further aspects include the array of devices allowing a linear fill factor greater than 80%, an array of magnets of alternating polarity arranged to provide the magnetic field for the array, and/or a center mirror array having no coils. In still further aspects of the invention, the second means for causing selective movement utilizes at least one electrode and the at least one coil and the at least one electrode can be in any position relative to each other on either side of the first and second axes. Also the at least one electrode may be positioned only on one side of the first axis, on one side of the second axis, and/or the at least one coil is positioned on the same said of the first axis as the at least one electrode. Additionally, the means for causing selective movement may utilize a common ground plane, an interposer, and/or at least one patterned electrode. Still further aspects include the array of devices allowing a linear fill factor greater than 80%, an array of magnets of alternating polarity arranged to provide the magnetic field for the array, and/or a center mirror array having no coils or electrodes. Further aspects include the at least one electrode may be used to sense rotation about at least one of the axes, a plurality of electrodes are used to measure differential capacitance for the second axis movement. Another aspect of the invention is that the mirror device has a double paddle structure.
In a further aspect of the present invention, an array of electromagnetically actuated MEMS devices is provided wherein each device includes a mirror with a reflective surface having no gimbal structure support, and at least one minor axis coil for causing selective movement of the mirror about the minor axis in the presence of a magnetic field. In still further aspects of the invention the minor axis coil produces dual axis rotation of the mirror and the array of mirror devices allows a linear fill factor greater than 80%.
Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from the description or recognized by practicing the invention as described in the written description and claims hereof, as well as the appended drawings.
It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview or framework to understanding the nature and character of the invention as it is claimed.
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiment(s) of the invention, and together with the description serve to explain the principles and operation of the invention.